1. Field of the Invention
The present invention relates to a plate for guiding light traveling therein, more particularly, to a light guide plate for providing light with uniform luminance distribution to be used for image display devices and a method of fabricating the light guide plate.
2. Description of the Related Art
A light guide plate is generally used inside a light equipment, or a backlight unit, that leads the light to a display equipment in an image display device. In a display device such as a liquid crystal display (LCD) device, a light guide plate is employed to guide and adjust paths of the light provided from a light source to produce light having uniform luminance distribution. Since liquid crystal in an LCD device emits no light, light is generated from a light source and then provided to the liquid crystal through a light guide plate.
An LCD device generally has a device for displaying images, a device for controlling the liquid crystal, and a device for supplying the light. The liquid crystal controlling device controls the transmission of light in the liquid crystal by applying electric field to liquid crystal molecules. In other words, applying electric field to the liquid crystal molecules will untwist them to varying degrees, depending on the current's voltage. LCD devices use such liquid crystal because it reacts predictably to electric current in such a way as to control light passage.
The light supplying device is to provide the liquid crystal with light having uniform brightness. The light supplying device has a light source and a light guide plate for producing the light. Typically, a light source in the light supplying device generates linear light having non-uniform optical distribution. Thus, the light guide plate converts such a light into planar light having uniform optical distribution to be provided to the liquid crystal. However, the conventional light guide plates have drawbacks such as decrease in the luminance on a display panel of the LCD device.
To increase the luminance, various types of light guide plates have been developed such as a light guide plate having diffusion dots on its reflection surface to increase the quantity of light exiting the light guide plate, as known to those skilled in the art.
Also, the light traveling in the light guide plate may be reflected by one surface of the light guide plate and exits another surface of the light guide plate. In this case, under the Snell's refraction law, the light exiting the light guide plate cannot have an exit angle perpendicular to the light exit surface of the light guide plate. It results in a decrease of the luminance on a display panel of the LCD device.
In order to make the light exit angle greater (i.e., closer to 90°), the conventional light supplying devices employ various types of optical sheets on the light guide-plate. For instance, a diffusion sheet is disposed on the light guide plate to increase the light exit angle, and a prism sheet is further disposed on the diffusion sheet to increase an exit angle of the light exiting the diffusion sheet.
Although the diffusion sheets and prism sheets may enhance the luminance on a display panel of the LCD device, they causes such problems as increasing the overall weight and volume of an LCD device and also increasing the manufacturing cost of an LCD device because of the additional components.
Therefore, a need exists for a light guide plate for maximizing the luminance on a display panel of an LCD device without increasing the number of components for the LCD device. Further, it will be advantageous to provide a method of fabricating such light guide plates in a simpler process and in a mass production process.